Shiny app that fetches data via URL works locally but not on shinyapps.io

Question

I wrote a simple shiny app to illustrate a problem I am having fetching data from a website. Here is the UI code:

library(shiny)

shinyUI(fluidPage(

# Application title
titlePanel("Test App"),

# Sidebar with slider inputs 
sidebarLayout(
    sidebarPanel(
        actionButton("button", "Fetch Data")
                ),


    mainPanel(
        tabsetPanel(
            tabPanel("Data", textOutput("crimelist"))
        )
    )
  )
 )
)

And here is the Server code:

library(shiny)

# Define server logic 
shinyServer(function(input, output, session) {

    # Get a list of the different types of crime
    observeEvent(input$button, {
        url <- "https://phl.carto.com/api/v2/sql?format=csv&q=SELECT 
               distinct rtrim(text_general_code) as text_general_code
                            FROM incidents_part1_part2
                            order by text_general_code"
    crimelist <- read.csv(url(url), stringsAsFactors = FALSE)$text_general_code
    output$crimelist <- renderText({crimelist})
    })
})

The data being fetched is described at https://cityofphiladelphia.github.io/carto-api-explorer/#incidents_part1_part2.

When I run this shiny app in my local environment, it works perfectly. When publish it to shinyapps.io and run it, the application fails when I click the button to fetch the data. In the shiny log, it reports the following:

2017-10-11T14:46:31.242058+00:00 shinyapps[224106]: Warning in 
open.connection(file, "rt") :
2017-10-11T14:46:31.242061+00:00 shinyapps[224106]:   URL 'https://phl.carto.com/api/v2/sql?format=csv&q=SELECT distinct 
rtrim(text_general_code) as text_general_code
2017-10-11T14:46:31.242062+00:00 shinyapps[224106]: FROM incidents_part1_part2
2017-10-11T14:46:31.242063+00:00 shinyapps[224106]: order by text_general_code': status was 'URL using bad/illegal format or missing URL'
2017-10-11T14:46:31.243062+00:00 shinyapps[224106]: Warning: Error in open.connection: cannot open connection

I am really stumped - is this a shiny server issue of some kind? If anyone out there has a clue, I am all ears!

score 3 · Answer 1 · edited Jun 20 '20 at 09:12

I posted this question on multiple boards, and Joshua Spiewak on the Shinyapps.io Users Google group solved my problem:

You need to encode the URL in order for it to be valid, e.g. https://phl.carto.com/api/v2/sql?format=csv&q=SELECT%20distinct%20rtrim(text_general_code)%20as%20text_general_code%20FROM%20incidents_part1_part2%20order%20by%20text_general_code

shinyapps.io runs on Linux, so it is likely that curl is being used to fetch this URL. My guess is that you are using Windows locally, which uses a less strict mechanism that is tolerant of the spaces and newlines you have in the URL.

After making his suggested change, it works as expected now. Thanks, Joshua!

Shiny app that fetches data via URL works locally but not on shinyapps.io

1 Answers1